Documentation: core-api: entry: Replace deprecated KVM entry/exit functions

The x86-specific functions kvm_guest_{enter,exit}_irqoff() were removed
and replaced by the generic guest_state_{enter,exit}_irqoff() in commit
ef9989a ("kvm: add guest_state_{enter,exit}_irqoff()") and commit
b2d2af7 ("kvm/x86: rework guest entry logic").

Update the references in the entry/exit handling documentation.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Nicolas Saenz Julienne <nsaenz@amazon.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20250723075134.105132-1-ajd@linux.ibm.com

Author: ajdlinux

Documentation/core-api/entry.rst

@@ -115,8 +115,8 @@ Entering or exiting guest mode is very similar to syscalls. From the host
 kernel point of view the CPU goes off into user space when entering the
 guest and returns to the kernel on exit.
 
-kvm_guest_enter_irqoff() is a KVM-specific variant of exit_to_user_mode()
-and kvm_guest_exit_irqoff() is the KVM variant of enter_from_user_mode().
+guest_state_enter_irqoff() is a KVM-specific variant of exit_to_user_mode()
+and guest_state_exit_irqoff() is the KVM variant of enter_from_user_mode().
 The state operations have the same ordering.
 
 Task work handling is done separately for guest at the boundary of the